Method and apparatus for producing simultaneously milled and stretched plastric strap

ABSTRACT

An apparatus and method for producing an oriented plastic strap having a predetermined desired thickness for use in strapping packages and the like is passed between a pair of cylinders or rollers placed closely together at a desired nip for reducing the thickness of the sheet. One roller is rotated at a faster lineal rate of speed than the other, and the rollers rotate in opposite directions. This apparatus and method achieves milling and stretching of the material substantially simultaneously at the nip of the rollers.

This application is a division of application Ser. No. 07/958,803, filedOct. 9,1992 now pending.

FIELD OF THE INVENTION

The present invention is directed to a method and apparatus forproducing an oriented plastic strap and more particularly to a methodand apparatus for milling and stretching a plastic sheet into strapstock material having a predetermined desired thickness.

BACKGROUND OF THE INVENTION

In a typical prior art stretching method, such as a SIGNODE® process, acast sheet of thermoplastic material, for example, polypropylene, isfirst reduced in size by rolling it through a pair of closely spacedmilling rollers or cylinders that rotate in opposite directions. Afterthe thickness of the sheet is reduced, the sheet is drawn and stretchedout of the milling rollers by a series of orienting rollers or a bridleassembly to its final desired size.

Another prior art method that is commonly used is a process called theshort gap method and is generally comprised of an entry bridle, astretching assembly and an exit bridle. A slow speed, heated bridleassembly advances a cast sheet of material, usually film, to astretching assembly. The stretching assembly is comprised of a pair ofrollers or cylinders set a distance apart. The first roller rotates atthe same speed as the entry bridle. The second roller is rotating fasterthan the first roller and at the same speed as the exit bridle. Thus, asthe film passes through the assembly, it is stretched to its finaldesired size

These prior art methods present several disadvantages. The properties ofthe strap produced by these methods provide limited increases instrength without significant decreases in other desired properties.Also, substantial necking occurs as the sheet is stretched over thedistance between the rollers.

The present invention presents a novel milling and stretching apparatusand method intended to minimize these problems, as well as to presentseveral other improvements.

OBJECTS OF THE INVENTION

A general object of the present invention is to provide a novelapparatus and method for producing oriented plastic strap.

Another object of the present invention is to provide a novel apparatuscapable of milling and stretching a workpiece into a strap having apredetermined desired thickness in a single pass through a single pairof rollers.

It is a further object of the present invention to provide a novelmethod and apparatus for producing oriented plastic strap havingsignificantly increased tensile strength and resistance to splitting ascompared to straps produced by heretofore known methods and apparatus.

It is a specific object of the present invention to provide a strap witha high tensile strength, high resistance to splitting and improvedwelding characteristics.

SUMMARY OF THE INVENTION

Briefly, and in accordance with the foregoing, the present inventioncomprises an apparatus and method for producing an oriented plasticstrap having a predetermined desired thickness for use in strappingpackages and the like. A plastic workpiece or sheet is passed between apair of cylinders or rollers placed closely together at a desired nipfor reducing the thickness of the sheet. One roller is rotated at afaster lineal rate of speed than the other, and the rollers rotate inopposite directions. This apparatus and method therefore achievesmilling and stretching of the material substantially simultaneously atthe nip of the rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

The organization and manner of the structure and operation of theinvention, together with further objects and advantages thereof, maybest be understood by reference to the following description, taken inconnection with the accompanying drawings, wherein like referencenumerals identify like elements throughout the several views in which:

FIG. 1 is a simplified fragmentary front view of an apparatus forproducing oriented plastic strap according to the present invention;

FIG. 2 is an enlarged simplified front view of the milling andstretching rollers shown in FIG. 1;

FIG. 3 is an enlarged partial cross-sectional view of FIG. 1 taken alongline 3--3 of FIG. 1, and

FIG. 4 is a simplified reduced fragmentary partial sectional view of themilling and stretching roller system without the sheet of plastic asseen along a line or direction parallel to line 3--3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the invention may be susceptible to embodiment in different forms,there is shown in the drawings, and herein will be described in detail,a specific embodiment with the understanding that the present disclosureis to be considered an exemplification of the principles of theinvention, and is not intended to limit the invention to that asillustrated and described herein.

As illustrated schematically in FIG. 1, the present invention includes azero gap assembly 20 for milling and stretching or elongating a sheet orworkpiece 22 into a thin strap stock material. The present invention isdiscussed with only a single sheet or workpiece 22, however, it is to beunderstood that more than one sheet or workpiece 22 may be passedthrough the assembly at a time. The phrase "zero gap" as used hereinrefers to the concept of substantially eliminating any gap between astep of milling and a step of stretching a sheet or workpiece. In otherwords, the steps of milling and stretching are accomplishedsubstantially simultaneously. The zero gap assembly 20 is locatedbetween a feeding assembly 24 and an exit bridle assembly 26 on a frameor support 28.

The feeding assembly 24 may take any one of several forms, and as shownin FIG. 1, includes an extruding machine 30 for extruding a sheet orworkpiece 22 of stock material and an entry bridle assembly 32.

The extruding machine 30 produces a sheet or workpiece 22 of suitablematerial, such as polypropylene and the like, to the entry bridleassembly 32 for feeding into the zero gap assembly 20. The sheet 22 mayalso be pre-heated in the entry bridle assembly 32 in order to enhancethe working properties of the sheet material.

The entry bridle assembly 32 includes a plurality of rollers orcylinders 34, 36, 38 and 40 mounted by suitable means, such as a shaft,not shown, on the frame or support 28. The rollers 34, 36, 38 and 40 maybe solid or hollow. In the preferred embodiment, as shown in thefigures, the rollers 34, 36, 38 and 40 are essentially only used toproperly deliver the sheet 22 for feeding into the zero gap assembly 20,and do not substantially contribute to the stretching or the milling ofthe sheet 22. A different number of rollers may be employed than theamount shown in FIG. 1. The rollers 34, 36, 38 and 40 are arranged alongtwo rows with bottom row rollers 36 and 40 being spaced between and at adistance beneath the top row rollers 34 and 38. Rollers 34 and 38 rotatein a clockwise direction while rollers 36 and 40 rotate in acounterclockwise direction so that when the sheet 22 is wound around theentry bridle assembly 32, it travels through the rollers 34, 36, 38 and40. Each of the rollers 34, 36, 38 and 40 are rotated at a uniform speedby suitable means, not shown, such as a motor and shaft assembly. All Ofthe rollers 34, 36, 38 and 40 rotate at essentially the same speed orlineal surface velocity as a top roller 42 in the zero gap assembly 20which will be discussed in greater detail herein.

After the sheet 22 passes through the feeding assembly 24, it advancesto the zero gap assembly 20 for milling and stretching into a finishedsheet 22 having a predetermined desired thickness. The zero gap assembly20 includes a pair of rollers or cylinders 42 and 44 that are rotatablymounted in opposing relationship. The nip 46, that is, the minimumdistance between the rollers 42 and 44, can be varied greatly dependingon the desired finished thickness of the sheet 22.

The zero gap rollers 42 and 44 may be solid or hollow and may be heatedby well-known means, not shown, such as circulating a heated fluidwithin the roller 42 or 44, in order to enhance the stretchingproperties of the sheet material. The zero gap rollers 42 and 44 mayalso be flat, as shown in the figures, or shaped in order to change theshape of the sheet 22 as it passes through the rollers 42 and 44.

As best shown in FIG. 2, the top roller 42 is driven in a clockwisedirection, as shown by an arrow, and the bottom roller 44 is driven in acounterclockwise direction, as shown by an arrow. The sheet 22 firstfeeds around a portion of the top roller's 42 circumference, thenthrough the nip 46 defined between the rollers 42 and 44, and thenaround a portion of the bottom roller's 44 circumference. The sheet 22contacts over half of the circumference of each one of the rollers 42and 44 as it passes around the rollers 42 and 44. Each roller 42 and 44contacts an opposite side of the sheet 22.

In the preferred embodiment, as shown in the figures and as described indetail herein, the mill rollers 42 and 44 are situated in a top-bottomarrangement. However, it is to be understood that the rollers 42 and 44may be placed in a side-by-side arrangement. In a side-by-sidearrangement, the top roller 42 becomes the first roller the sheetcontacts while the bottom roller 44 becomes the second roller the sheetcontacts.

As best shown in FIG. 4, the zero gap rollers 42 and 44 are respectivelyconnected to shafts 48 and 50 fixed to their centers 52 and 54. Drivemeans 56 and 58, such as electric motors, are mounted on the support 28and drive the rollers 42 and 44, respectively, through shafts 60 and 62that are connected to shafts 48 and 50 by a coupling 64 and 66,respectively. Coupling 66 may take the form of a universal coupling. Thebottom roller 44 is connected to the support 28 by bearings 68 and 70.The coupling 66 and the bearings 68 and 70 allow the bottom roller 44 tomove in relation to the support 28 by actuators 72 and 74. This allowsthe bottom roller 44 to be moved toward and away from the stationary toproller 42 thus changing the size of the nip 46. Each of the shafts 48and 50 is driven independently by its separate drive means 56 and 58,and the bottom roller 44 is driven at greater speed. More specifically,the roller 44 is driven so that its lineal surface velocity ispreferably within the range of seven to twelve times faster than thelineal surface velocity of the top roller 42.

Thus, as the sheet 22 passes through the nip 46, the top roller 42operates as a brake, and the mill reduction may also act as a brake, onthe lower surface of the sheet 22 while the bottom roller 44 pulls andaccelerates the sheet 22. As the sheet 22 accelerates through the nip46, it is simultaneously milled and stretched to its final predeterminedthickness as it passes through the nip 46. The desired finished sheet 22exits the nip 46 with a thickness which may be less than the dimensionof the nip 46. The thickness of the finished sheet 22 depends on thelineal surface velocity differential between the top roller 42 and thebottom roller 44. The faster the bottom roller 44 rotates, the thinnerthe finished sheet 22 will be. Some stretching may occur slightly beforeor after the nip 46 depending on the velocity of the bottom roller 44.Thus, there is essentially a zero gap between the milling and stretchingfunctions. One result is that there is substantially less necking of thesheet width in comparison to stretching methods in accordance with priorsuggested methods wherein the sheet is stretched only after the millingstep has been completed.

After the finished sheet 22 exits the zero gap assembly 20, it windsaround the exit bridle assembly 26. The exit bridle assembly 26 may takeany one of several forms, and as shown in FIG. 1, includes a pluralityof rollers or cylinders 76, 78, 80, 82, 84 and 86 mounted by suitablemeans, such as a plurality of shafts, not shown, on the support 28. Theyare used to pull the sheet 22 out of the zero gap assembly 20 properly.The rollers 76, 78, 80, 82, 84 and 86 may be solid or hollow. More orfewer rollers may be employed than the number shown in FIG. 1. Therollers 76, 78, 80, 82, 84 and 86 do not substantially contribute to anystretching of the sheet 22. The rollers 76, 78, 80, 82, 84 and 86 arearranged along two rows with bottom row rollers 78, 82 and 86 beingspaced between and at a distance beneath the top row rollers 76, 80 and84. Rollers 76, 80 and 84 rotate in a clockwise direction while rollers78, 82 and 86 rotate in a counterclockwise direction so that when thesheet 22 is wound around the exit bridle assembly 32, it travels throughthe rollers 76, 78, 80, 82, 84 and 86. The rollers 76, 78, 80, 82, 84and 86 are rotated at a uniform speed by suitable means, not shown, suchas a motor and shaft assembly. All of the rollers 76, 78, 80, 82, 84 and86 rotate at essentially the same lineal surface velocity as the bottomroller 44 in the zero gap assembly 20.

It is to be understood that another stretching step and apparatus, suchas a short gap stretch apparatus, may be used in the present inventionbefore or after the zero gap assembly 20 to further modify thecharacteristics of the sheet 22.

Having disclosed the specifics of the apparatus of the presentinvention, a method in accordance with the invention will now bediscussed.

The sheet 22 feeds from the extruding machine 30 to the entry bridleassembly 32 and winds around the entry bridle rollers 34, 36, 38 and 40for proper alignment for feeding into the zero gap assembly 20. Thesheet 22 then feeds around the top roller of the zero gap assembly 20.The top roller 42 and the entry bridle rollers 34, 36, 38 and 40 aredriven at the same lineal surface velocity.

As the sheet 22 enters the assembly 20, it travels around thecircumference of the top roller 42 until it reaches the nip 46 definedbetween the top and bottom rollers 42 and 44. The faster rotating bottomroller 44 pulls the sheet 22 through the nip 46 while the slowerrotating top roller 42 and the mill reduction brakes the speed of thelower surface of the sheet 22. Thus, the sheet 22 accelerates throughthe nip 46 and is simultaneously milled and stretched to its finalpredetermined thickness as it passes through the nip 46.

The exit bridle assembly 26 pulls the finished sheet 22 off of thebottom roller 44. This method produces a thin, flat oriented sheet 22that is now ready to be surface treated and/or heat treated as desiredand sliced into thin straps as required for use in strapping packagesand the like in accordance with known procedures.

The above described apparatus and method produce a significantly betterquality strap than prior art methods as illustrated in the table below.Each of the straps that were tested and are compared below areequivalent in material and thickness and have a width of 0.236 inches.The prior art "single draw" method strap referred to in the followingtable was produced by the SIGNODE® process using a milling step and thendrawing and stretching the material as it comes out of the millingrollers.

                  TABLE 1                                                         ______________________________________                                                       Single Draw                                                                            Zero Gap                                              ______________________________________                                        Tensile Strength KPSI                                                                          45         64                                                Elongation, %    25         13                                                Modulus @ 2 & 5 KPSI                                                                           400        963                                               Weld Strength Lbs.                                                                             79         187                                               Weld Percent     55         89                                                Weld Equivalent KPSI                                                                           25         57                                                Split In.        0.7        0.07                                              ______________________________________                                    

As shown in the table above, the zero gap method produces a highertensile strength strapping with a stronger and higher percentage weld.Furthermore, the splitting of the strap is essentially eliminated whilestill achieving a high tensile strength, whereas in current methods, asthe tensile strength is increased, more splitting results and percent ofweld strength decreases. Also, since the tensile strength of the zerogap method material is 1.47 times the standard strap and the elongationis about half of the standard strap, better creep performance isachieved.

This presents several market advantages in polypropylene materials.Specifically, if the pound's break strength of the strap is controllingthe application, then the higher tensile strength of the material willallow a substitution of a strap which involves only seventy percent ofthe currently used material. If stiffness is the controlling attribute,this method will produce a strap capable of being push-fed reliablyaround a guide chute of a strapping machine, and if weld strength is thecontrolling attribute, less than half of the currently used raw materialwill produce the equivalent pounds of joint strength.

The various properties resulting from this process give significantflexibility of design of a strap for a variety of applications. It isbelieved that the strap that is produced has a stronger bond across thegrain, while still being relatively easy to tear the strap across thegrain. Furthermore, the strap produced by the zero gap method does notfail a structural delamination test as do most prior art systems. Sincethe structural delamination of the strap does not fail, higher weldstrength is obtained.

If a pre-stretch step is used between the entry bridle and the zero gapassembly or if a post-stretch step is used between the zero gap assemblyand the exit bridle, the same overall characteristics are achieved asthe preferred embodiment described herein. A pre-stretch step, however,provides a more forgiving process and a higher tensile modulus can beachieved. A post-stretch step can provide material with greater tendencyto fibrillate.

While a preferred embodiment of the present invention is shown anddescribed, it is envisioned that those skilled in the art may devisevarious modifications of the present invention without departing fromthe spirit and scope of the appended claims. The invention is notintended to be limited by the foregoing disclosure. It is therefore tobe understood that within the scope of the appended claims, the presentinvention may be practiced otherwise than as specifically describedherein.

The invention claimed is:
 1. A plastic strap, made from a solid sheet ofmaterial having a predetermined original thickness dimension andsimultaneously milled and stretched by being passed through a nipdefined between a pair of opposed rollers which are spaced apart withrespect to each other so as to define said nip therebetween which has apredetermined space dimension which is substantially less than saidpredetermined original thickness dimension of said solid sheet ofmaterial, said pair of opposed rollers being simultaneously rotated inopposite directions at different lineal surface velocities such that afirst lineal surface velocity of a first one of said pair of opposedrollers, is within a range of seven to twelve times faster than a secondlineal surface velocity of a second one of said pair of opposed rollers,comprising:first surface means, of said solid sheet of material havingsaid predetermined original thickness dimension prior to entering saidnip defined between said pair of opposed rollers, for engaging therotating peripheral surface of said first one of said pair of opposedrollers having said first lineal surface velocity, and second surfacemeans, of said solid sheet of material having said predeterminedoriginal thickness dimension prior to entering said nip defined betweensaid pair of opposed rollers, for engaging the rotating peripheralsurface of said second one of said pair of opposed rollers having saidsecond lineal surface velocity, in such a manner that said solid sheetof material, having said predetermined original thickness dimensionprior to entering said nip defined between said pair of opposed,oppositely rotating rollers, is forced through said nip defined betweensaid pair of opposed, oppositely rotating rollers so as to besimultaneously milled and stretched within said nip defined between saidpair of opposed, oppositely rotating rollers during a single pass ofsaid solid sheet of material through said nip defined between said pairof opposed, oppositely rotating rollers, whereby said solid sheet ofmaterial, having passed through said nip defined between said pair ofopposed, oppositely rotating rollers and having said predetermined spacedimension which is substantially less than said predetermined originalthickness dimension of said solid sheet of material, has a finalizedthickness dimension, as a result of said simultaneous milling andstretching of said solid sheet of material within said nip definedbetween said pair of opposed, oppositely rotating rollers, which issubstantially less than said predetermined original thickness dimensionof said solid sheet of material before said solid sheet of materialentered said nip defined between said pair of opposed, oppositelyrotating rollers.
 2. The strap as set forth in claim 1, wherein:saidfinalized thickness of said solid sheet of material comprising saidstrap has a thickness dimension which is less than said predeterminedspace dimension defining said nip defined between said pair of opposed,oppositely rotating rollers.
 3. The strap as set forth in claim 1wherein:said solid sheet of material comprises polypropylene.
 4. Thestrap as set forth in claim 1, wherein:said strap exhibits tensilestrength characteristics which are substantially greater than tensilestrength characteristics of conventional straps produced by processescomprising non-simultaneous milling and stretching, wherein said tensilestrength characteristics of said conventional straps have a maximumvalue of 45,000 psi.
 5. The strap as set forth in claim 4, wherein:saidtensile strength characteristics of said strap has a value of 64,000psi.
 6. The strap as set forth in claim 4, wherein:said strap exhibitssplit resistance characteristics which are substantially less than splitresistance characteristics of said conventional straps when said tensilestrength characteristics of said strap are greater than said maximumtensile strength value of 45,000 psi characteristic of said conventionalstraps.
 7. The strap as set forth in claim 6, wherein:said splitresistance of said strap is 0.07 inches when said tensile strength valueof said strap is 64,000 psi.
 8. A plastic strap, made from a solid sheetof material having a predetermined original thickness dimension andsimultaneously milled and stretched by being passed through a nipdefined between a pair of opposed rollers which are spaced apart withrespect to each other so as to define said nip therebetween which has apredetermined space dimension which is substantially less than saidpredetermined original thickness dimension of said solid sheet ofmaterial, said pair of opposed rollers being simultaneously rotated inopposite directions at different lineal surface velocities such that afirst lineal surface velocity of a first downstream one of said pair ofopposed rollers, as considered in the direction of travel of said solidsheet of material through said nip defined between said pair of opposedrollers, is within a range of seven to twelve times faster than a secondlineal surface velocity of a second upstream one of said pair of opposedrollers as considered in said direction of travel of said solid sheet ofmaterial through said nip defined between said pair of opposed rollers,comprising:first surface means, of said solid sheet of material havingsaid predetermined original thickness dimension prior to entering saidnip defined between said opposed rollers, for engaging the rotatingperipheral surface of said second upstream one of said pair of opposedrollers having said second lineal surface velocity, and second surfacemeans, of said solid sheet of material having said predeterminedoriginal thickness dimension prior to entering said nip defined betweensaid pair of opposed rollers, for engaging the rotating peripheralsurface of said first downstream one of said pair of opposed rollershaving said first lineal surface velocity, in such a manner that saidsolid sheet of material, having said predetermined original thicknessdimension prior to entering said nip defined between said pair ofopposed, oppositely rotating rollers, is forced through said nip definedbetween said pair of opposed, oppositely rotating rollers so as to besimultaneously milled and stretched within said nip defined between saidpair of opposed, oppositely rotating rollers during a single pass ofsaid solid sheet of material through said nip defined between said pairof opposed, oppositely rotating rollers as a result of said secondupstream one of said pair of opposed rollers braking said solid sheet ofmaterial while said first downstream one of said pair of opposed rollersaccelerates said solid sheet of material in view of said differentlineal surface velocities of said pair of opposed rollers, whereby saidsolid sheet of material, having passed through said nip defined betweensaid pair of opposed, oppositely rotating rollers and having saidpredetermined space dimension which is substantially less than saidpredetermined original thickness dimension of said solid sheet ofmaterial, has a finalized thickness dimension, as a result of saidsimultaneous milling and stretching of said solid sheet of materialwithin said nip defined between said pair of opposed, oppositelyrotating rollers, which is substantially less than said predeterminedoriginal thickness dimension of said solid sheet of material before saidsolid sheet of material entered said nip defined between said pair ofopposed, oppositely rotating rollers.
 9. The strap as set forth in claim8, wherein:said finalized thickness of said solid sheet of materialcomprising said strap has a thickness dimension which is less than saidpredetermined space dimension defining said nip defined between saidpair of opposed, oppositely rotating rollers.
 10. The strap as set forthin claim 8, wherein:said solid sheet of material comprisespolypropylene.
 11. The strap as set forth in claim 8, wherein:said strapexhibits tensile strength values which are substantially greater thantensile strength values of conventional straps produced by processescomprising non-simultaneous milling and stretching process steps,wherein said tensile strength values of said conventional straps have amaximum value of 45,000 psi.
 12. The strap as set forth in claim 11,wherein:said tensile strength value of said strap is 64,000 psi.
 13. Thestrap as set forth in claim 11, wherein:said strap exhibits splitresistance values which are substantially less than split resistancevalues of said conventional straps when said tensile strength values ofsaid strap are greater than said maximum tensile strength value of45,000 psi of said conventional straps.
 14. The strap as set forth inclaim 13, wherein:said split resistance of said strap is 0.07 incheswhen said tensile strength value of said strap is 64,000 psi.
 15. Aplastic strap, made from a solid sheet of material having apredetermined original thickness dimension and simultaneously milled andstretched by being passed through a nip defined between a pair ofopposed rollers which are spaced apart with respect to each other so asto define said nip therebetween which has a predetermined spacedimension which is substantially less than said predetermined originalthickness dimension of said solid sheet of material, said pair ofopposed rollers being simultaneously rotated in opposite directions atdifferent lineal surface velocities such that a first lineal surfacevelocity of a first one of said pair of opposed rollers is within arange of seven to twelve times faster than a second lineal surfacevelocity of a second one of said pair of opposed rollers,comprising:first surface means, of said solid sheet of material havingsaid predetermined original thickness dimension prior to entering saidnip defined between said pair of opposed rollers, for engaging a firstcircumferential portion of said first one of said pair of opposedrollers having said first lineal surface velocity wherein said firstcircumferential portion of said first one of said pair of opposedrollers comprises a circumferential extent which is greater thanone-half of the circumference of said first one of said pair of opposedrollers, and second surface means, of said solid sheet of materialhaving said predetermined original thickness dimension prior to enteringsaid nip defined between said pair of opposed rollers, for engaging asecond circumferential portion of said second one of said pair ofopposed rollers having said second lineal surface velocity wherein saidsecond circumferential portion of said second one of said pair ofopposed rollers comprises a circumferential extent which is greater thanone-half of the circular cumference of said second one of said pair ofopposed rollers, in such a manner that said solid sheet of material,having said predetermined original thickness dimension prior to enteringsaid nip defined between said pair of opposed, oppositely rotatingrollers, is forced through said nip defined between said pair ofopposed, oppositely rotating rollers so as to be simultaneously milledand stretched within said nip defined between said pair of opposed,oppositely rotating rollers during a single pass of said solid sheet ofmaterial through said nip defined between said pair of opposed,oppositely rotating rollers, whereby said solid sheet of material,having passed through said nip defined between said pair of opposed,oppositely rotating rollers and having said predetermined spacedimension which is substantially less than said predetermined originalthickness dimension of said solid sheet of material, has a finalizedthickness dimension, as a result of said simultaneous milling andstretching of said solid sheet of material within said nip definedbetween said pair of opposed, oppositely rotating rollers, which issubstantially less than said predetermined original thickness dimensionof said solid sheet of material before said solid sheet of materialentered said nip defined between said pair of opposed, oppositelyrotating rollers.
 16. The strap as set forth in claim 15, wherein:saidfinalized thickness of said solid sheet of material comprising saidstrap has a thickness dimension which is less than said predeterminedspace dimension defining said nip defined between said pair of opposed,oppositely rotating rollers.
 17. The strap as set forth in claim 15,wherein:said solid sheet of material comprises polypropylene.
 18. Thestrap as set forth in claim 15, wherein:said strap exhibits tensilestrength values which are substantially greater than tensile strengthvalues of straps produced by processes comprising non-simultaneousmilling and stretching process steps, wherein said tensile strengthvalues of said straps produced by said processes have a maximum value of45,000 psi.
 19. The strap as set forth in claim 18, wherein:said tensilestrength value of said strap is 64,000 psi.
 20. The strap as set forthin claim 18, wherein:said strap exhibits split resistance values whichare substantially less than split resistance values of said strapsproduced by said processes when said tensile strength values of saidstraps are greater than said maximum tensile strength value of 45,000psi of said straps produced by said processes.
 21. The strap as setforth in claim 20, wherein:said split resistance value of said strap is0.07 inches when said tensile strength value of said strap is 64,000psi.